This invention relates to a method of and apparatus for protecting and improving the water quality of substantially enclosed bodies of fresh water such as reservoirs of water to be used as a source of domestic water employing the phenomena of biodegradation to eliminate bacteria.
Reservoirs of water to be used for domestic purposes are of small size as compared to large areas of water that may be termed lakes, bays, sounds, etc. The land area surrounding reservoirs are generally termed water shed areas in reference to water run off due to rainfall. Water companies and water supply organizations go to great lengths to protect water shed areas from contaminants that will be carried in rainfall run-off or discharge into a reservoir. In some cases surface water discharge may be from storm drains that collect surface water from a very large area that cannot be managed by a water company. Rain fall and resulting surface storm water run off picks up and carries contaminants including both animal and human fecal matter particulate into a reservoir increasing the coliform count in the water and the turbidity of the water which threatens the quality of water supplied to domestic users. Such storm water also carries non-organic particles into the reservoir.
This has led to the necessity of providing filtration plants for water that is drawn from the reservoir and eventually supplied to domestic users. Additionally, chemical treatment of the water (chlorination) or with disinfectant by products harmful to a few may be necessary to kill bacteria. The cost of filtration plants is very high but they must be used where necessary to meet various standards and regulations applicable to the purity of domestic water. For example, to avoid filtration a public water system that uses surface water sources must have source water quality where the fecal coliform concentration is equal to or less than 20/100 milliliter (ml), or the total coliform concentration must be equal to or less than 100/100 ml in representative samples of the source water immediately prior to the first or only point of disinfectant application in at least ninety percent (90%) of the measurements made in the previous six months that the system served water to the public. In addition the turbidity level cannot exceed five (5) nephelometric turbidity units (NTU) in representative samples of the source water immediately prior to the first or only point of disinfectant application. This standard is known as Criteria for Filtration Avoidance and if not met, the construction and use of filtration facilities is mandated by the Safe Water Drinking Act.
The present invention provides an alternative to the necessity of filtration plants in many instances and at small fractions of the cost of a filtration plant. As hereinafter described in more detail the present invention and/or discovery utilizes a floating boom support for a separator curtain which provides a filter for water run off and discharge into the main body of a reservoir.
The use of floating booms to isolate small bodies of water from or in large bodies of water is well known. A common floating boom structure which has been used for such purposes is shown in U.S. Pat. No. 5,102,261. Such booms or variations thereof may be used in practice of the present invention. The term xe2x80x9cboomxe2x80x9d is believed to have been first used in logging applications where a series of logs were tied together in a river or large stream to surround other logs and keep them from individually floating away while awaiting transport to a mill. Today the term xe2x80x9cboomxe2x80x9d is applied to many systems for various purposes, as for example oil spill containment booms.
Booms of the type disclosed in U.S. Pat. No. 5,102,261 have been used for many purposes. Such a boom has also been used to prevent entraining fish in electric generating plant cooling water intakes from river water; to serve as a barrier about dredging operations and to protect areas such as salmon spawning areas from oil spills. Such booms have also been used to block particulate matter and marine life from beach bathing areas. This last mentioned application has resulted in the lowering of coliform in the protected area only by blocking the particulate matter upon which microorganisms are carried, but did not utilize the present invention.
These previously known uses of boom supported filters has been to block particulate matter and/or marine life matter from entering a predetermined area or to confine particulate matter from entering a given area. This is primarily by filtering particulate matter and preventing or reducing turbidity in a boom protected area.
It has now been discovered that sizing a confined area of water hereinafter referred to as a surface water entrance basin, that receives run off or discharge of surface water into a body of water, such as a reservoir, and permitting only a controlled volumetric rate of passage of water from the entrance basin through a filter curtain produces concentration of biodegradable organic material at the filter curtain. The increased microbial density at the filter curtain results in biodegradation of particulate organic matter by the microorganisms carried by such particulate matter. The controlled volumetric rate of passage further inhibits impingement of any particulate matter upon the filter curtain with a force that would tend to hold such particulate matter against and tend to clog the filter openings.
An object of this invention is to provide a new and improved method of and apparatus for reducing the bacteria (coliform) count in water drawn from a reservoir and used for domestic purposes.
Another object of this invention is to provide a new and improved method of and apparatus for improving the water quality of the contents of a reservoir and avoid construction of filtration facilities or upgrading of existing filtration plants.
A further object of this invention is to provide a method of and apparatus for improving the quality of water in a reservoir by confining rain and storm water discharge in a water entrance basin in the reservoir within a floating boom filter and accelerating biodegradation of organic material introduced into a surface water entrance basin at the filter.
Briefly stated the invention in one form thereof, comprises identifying areas of surface water run-off and/or points of storm water discharge into bodies of fresh water such as a reservoir. Such areas termed surface water entrance basins are delineated by provision of floating booms to separate such surface water entrance basins from the main body of a reservoir. Supported from the booms is a curtain of geosynthetic fabric material that is anchored to the floor of the reservoir along the profile of the reservoir floor. The fabric material has openings of substantially twenty (20) microns as determined by particle size analysis in water. The run off contains organic particulate matter that is a carrier of microorganisms as small as one micron. The filtering nature of the sheet fabric prevents passage of the particulate matter and turbidity causing particles. This greatly concentrates organic and fecal particulate matter and microbial density increases. The concentrated organic matter provides a source of nourishment for the microorganisms. The microorganisms or bacteria feed upon and decompose the biodegradable organic particulate matter into its constituents, primarily releasing carbon dioxide thus and clarifying the ground surface water run-off before it enters the main body of water. The concentration of microorganisms consume and biodegrade the organic material trapped by the fabric sheet and ultimately expire as the biodegradable organic matter is consumed. This biodegradation is caused by controlling the rate of flow through the filter fabric thus concentrating the particulate organic matter at the filter fabric. The microorganisms multiply with the concentration of food and consume the organic matter. As the food supply diminishes, the microorganisms expire and become sediment. These results in eliminating or substantially lowering the bacteria count in the main body of water due to entrance of surface water and/or storm water discharge. The low flow rate through the filter causes particulate matter striking the filter to fall off rather than remain on the filter curtain and clog the openings. The invention is also applicable to the entrance points of streams or brooks that have received surface water run-off and which feed into the body of water to be protected.
The invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. The invention, however, together with further objects and advantages thereof may be best appreciated by reference to the following detailed description taken in conjunction with the drawings.